import java.util.Scanner;

public class Test2 {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        System.out.println(sumPrint(n));
    }
    public static int sumPrint(int n) {
        int sum = 0;
        int ret = 1;
        for (int i = 1; i <= n ; i++) {
          ret *= i;
          sum += ret;
        }
        return sum;
    }
    public static void main8(String[] args) {
        Scanner scan = new Scanner(System.in);
        System.out.print("请输入两个整数：");
        int a = scan.nextInt();
        int b = scan.nextInt();
        System.out.print("请输入三个小数：");
        float f1 = scan.nextFloat();
        float f2 = scan.nextFloat();
        float f3 = scan.nextFloat();
        System.out.println("最大值为："+ max(a,b));
        System.out.println("最大值为："+ max(f1,f2,f3));
    }
    public static int max(int a,int b) {
        return a > b ? a : b;
    }
    public static float max(float f1,float f2,float f3) {
        float max = f1;
        if(max < f2) {
            max = f2;
        }
        if(max < f3) {
            max = f3;
        }
        return max;
    }

    public static void main7(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        System.out.println(sum(n));
    }
    public static int sum(int n) {
        if(n == 1) {
            return 1;
        }else {
            int ret = sum(n -1) + n;
            n--;
            return ret;
        }
    }
    public static void main6(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        System.out.println(fac(n));
    }
    public static int fac(int n) {
        if(n == 1) {
            return 1;
        }else {
            return n * fac(n - 1);
        }
    }
    public static void main5(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        System.out.println(fib(n));
    }
    public static int fib(int n) {
        if(n <= 2) {
            return 1;
        }else {
            return fib(n-1) + fib(n-2);
        }
    }
    public static void main4(String[] args) {
        Scanner scan = new Scanner(System.in);
        int n = scan.nextInt();
        int ret = func(n);
        System.out.println(ret);
    }
    public static int func(int n) {
        if(n >= 0 && n <= 9) {
        return n;
        }else {
            int ret = func(n / 10) + n % 10;
            n /= 10;
            return ret;
        }
    }
    public static void main3(String[] args) {
        Scanner scan = new Scanner(System.in);
        int input = scan.nextInt();
        print(input);
    }
    public static void print(int n) {
        if(n >= 0 && n <= 9) {
            System.out.print(n +" ");
        }else {
            print(n / 10);
            System.out.print(n % 10 +" ");
            n /= 10;
        }
    }
    public static void main2(String[] args) {
        Scanner scan = new Scanner(System.in);
        int input = scan.nextInt();
        print(input);
    }
    public static void main1(String[] args) {
        Scanner scan = new Scanner(System.in);
        int a = scan.nextInt();
        int b = scan.nextInt();
        int c = scan.nextInt();
      //System.out.println(max(a, b));
        System.out.println(max(a, b, c));
    }
//    public static  int max(int a,int b) {
//        int ret = a > b ? a : b;
//        return ret;
//    }
    public static int max(int a,int b,int c) {
        int max= a;
        if (max < b) {
            max = b;
        }
        if (max < c) {
            max = c;
        }
        return max;
    }
//    public static  void print(int n) {
//        if (n >= 0 && n <= 9) {
//            System.out.print(n+" ");
//        } else {
//            print(n / 10);
//            System.out.print(n % 10 +" ");
//            n /= 10;
//        }
//    }
}
